Previous studies on the relationship between olfaction and depression have revealed mixed results. In addition, few have focused on the reciprocity of this association. The aim of this study is to combine depression and olfactory data in two separate patient populations to further understand their association. A systematic literature review was conducted using 3 online databases to identify studies correlating olfaction and depression in patients presenting with either primary depression or primary olfactory dysfunction. For the depressed population, weighted means and standard deviations for the Sniffin' Sticks Test and the 40-item Smell Identification Test were combined using 10 studies. For the olfactory dysfunction population, weighted means of Beck's Depression Inventory were combined using 3 studies. Independent t-tests were used to compare differences between groups. Comparing primary depressed patients with controls, depressed patients showed decreased scores in olfactory threshold (6.31±1.38 vs. 6.78±0.88, P = 0.0005), discrimination (12.05±1.44 vs. 12.66±1.36, P = 0.0073), identification (12.57±0.74 vs. 12.98±0.90, P < 0.0001), and 40-Item Smell Identification Test (35.31±1.91 vs. 37.41±1.45, P < 0.0001). In patients with primary olfactory dysfunction, Beck's Depression Inventory scores were significantly different between patients classified as normosmics, hyposmics and anosmics (5.21±4.73 vs. 10.93±9.25 vs. 14.15±5.39, P ≤ 0.0274 for all 3 comparisons). In conclusion, patients with depression have reduced olfactory performance when compared with the healthy controls and conversely, patients with olfactory dysfunction, have symptoms of depression that worsen with severity of smell loss.

Objective Many studies have reported that olfactory dysfunction frequently occurs in chronic rhinosinusitis (CRS) populations; however, the prevalence and degree of olfactory loss has not been systematically studied. The aims of this study are to use combined data to report the prevalence of olfactory dysfunction and to calculate weighted averages of olfactory test scores in CRS patients. Data Sources A search was conducted in PubMed and Scopus, following the methods of Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines. Review Methods Studies reporting the prevalence of olfactory dysfunction using objective measures or olfactory test scores using validated scales were included. Results A total of 47 articles were included in systematic review and 35 in the pooled data analysis. The prevalence of olfactory dysfunction in chronic rhinosinusitis was found to be 30.0% using the Brief Smell Identification Test, 67.0% using the 40-item Smell Identification Test, and 78.2% using the total Sniffin’ Sticks score. Weighted averages ± standard deviation of olfactory test scores were 25.96±7.11 using the 40-item Smell Identification Test, 8.60±2.81 using the Brief Smell Identification Test, 21.96±8.88 using total Sniffin’ sticks score, 5.65±1.51 using Sniffin’ Sticks threshold, 9.21±4.63 using Sniffin’ Sticks discrimination, 9.47±3.92 using Sniffin’ Sticks Identification, and 8.90±5.14 using the questionnaire for olfactory disorders-negative statements. Conclusion In chronic rhinosinusitis populations, a significant percentage of patients experience olfactory dysfunction and mean olfactory scores are within the dysosmic range.

ABSTRACT

Endoscopic sinus surgery improves nearly all subjective and objective measures of olfaction in chronic rhinosinusitis patients. Patients with nasal polyposis or preoperative olfactory dysfunction improve to a greater degree.

Background: Volumetric analysis of the olfactory cleft by using computed tomography has been associated with olfaction in patients with chronic rhinosinusitis (CRS)